Dampers for axial flow blades



June 10,1958 E. A. STALKER 2,838,273

' DAMPERS FOR AXIAL FLOW BLADES Filed 001:. 22, 1954 2 Sheets-Sheet 1 IN V EN TOR.

June 10, 1958 E. A STALKER DAMPERS FOR AXIAL mow BLADES 2' Sheets-Sheet 2 Filed Oct. 22, 1954 m w m m United States PatentO DAMPERS FOR AXIAL FLOW BLADES Edward A. Stalker, Bay City, Mich., assignor to The Stalker Development Company, Bay.City, Mich, a corporation of Michigan Application October 22,1954, Serial No. 463,976

4 Claims. 01. 253-77 Thisiinvention relatesto compressors, turbines and the like and particularly to the blading thereof.

An object of the'invention is to provide an effective damping means for the blades.

Another object is to provide a damping means particularly suited to sheet metal blades.

Other objects will be apparent from the specification, drawingsand claims. I

The above objects are accomplished by means illustrated in the accompanying drawings in which- Fig. 1 is a fragmentary axial section through a compressor incorporating rotors whose blades are damped by the means of this invention;

Fig. 2 is a fragmentary axial section through the rim of the rotor hub on line 2-2 in Fig. 3;

1 Fig. 3 is a fragmentary section on .line 3- 3: in Figs. 1 and Fig. 4 is a diagrammatic transverse section of a blade;

Fig. 5 is a fragmentary section on line 5-5 in Fig. 3;

Fig. 6 is -an enlarged view of part of the damper mechanism shown with a fragment of the hub rim;

Fig. 7 is a section on line 77 in Fig. 6; and

Fig. 8 is a sectional view on the line 8-8 of Fig. 2.

Referring now to the drawing, particularly Fig. l, the compressor is indicated generally as 10. It comprises the case 12 and the rotor assembly 14. The case has the annular inlet 16 for the admission of fluid and the annular exit 18.

The rotor assembly is mounted in the case by shafts 20 and 22 rotatably supported in bearings 24 and 26.

The rotor assembly comprises the rotors -34. Since these are substantially alike, rotor 30 will be described in detail as representative of all said rotors.

Each rotor, as shown particularly in Figs. 1-3 includes a hub structure comprising a disk 40, and a rim 42 having side flanges 43 and 43a, the hub structure supporting a plurality of axial flow blades 46 spaced peripherally about the rim. 7

Each blade has the hollow envelope 50 enclosing the stem means comprising the front and rear stem parts 53 and 54 respectively. These stem parts extend inward from the lower edge of the blade envelope and are fixed to opposite sides of the disk 40. The front stem part 53 on one side thereof has a portion extending forward forming the flange 64 fixed to the rim for its support. The other side of the front stem part is tapered toward the disk. The rear stem part 54 has both sides tapered toward the disk as shown in Fig. 2.

The rim 42 is further supported by the channel fixed to the rim and to the disk. See Fig. 3.

Preferably each blade section is substantially curved along the chord (Figs. 3 and 4) so that the general direction of the rear portion is more nearly parallel to the axis of rotor rotation than to the tangent 72 to the mean camber line 73 at a locality adjacent the leading edge, L. E., of the blade.

Each blade tends to vibrate about a line through the centroid 81 of a'root section 82 of the blade, that is,

Thus the curvature of theblade and the fact, that a section through the blade at the inner or root end thereof has a substantial curvature, along its chord facilitates the damping of the blade by providing for damping means within the blade. The blade sections at various radial levels along the blade span are normally oriented' so that a connecting element 90, Figs. 2-4, can extend inside the blade from apoint 92 near the center of the tip chord to a point 94 near the trailing edge of the root section. This element will resist the displacement of the blade tip' away from the direction of rotation, that is toward the convex side of the blade. V a

The connecting element is preferably fixed to the convex side of the blade section at the outer or tip end and at the inward end is displaced toward the direction of rotation.

The element emerges from the blade and extends to the .damper means 98-passing along agroove 100 of the main body part 99 of said means, the groove being formed between two arms 101 extending outwardly from the main body 99. See Figs. 2, .6 and 7. The damper part 99 is hinged to the bracket 102 by pm 104 and the bracket is fixed to the flange 43 of the rim means. The element 90 is fixed to the pin 104 near the center thereof.

The brake is supported at one end 111 on the rim and is operably related to the damper by being pressed against part 99 of the damper by centrifugal force when the rotor is rotating. Friction between the brake 110 and part 99 damps its movement and the'vibration of the blade. Centrifugal force acts to keep the part 99 tightly against the element 90.

When the blade tip swings away from the direction of rotation the element 90 tends to become straight (see dashed line position of element 90 in Figs. 2 and 7) and rotates the damper part 99 about the pin against centrifugal force acting on the damper part. The brake dissipates the energy of movement of part 99 and accordingly damps the vibration of the blade also.

The inertia of the element 90 and part 99 also provides damping of each blade, even without the eflect of the brake part.

It will now beclear that the invention provides very effective damping of the vibration of the blades and has the further advantage of being within the blades where no adverse effect can extend to the flow of fluid.

While I have illustrated specific forms of the invention, it is to be understood that variations may be made therein and that I intend to claim my invention broadly as indicated by the appended claims.

I claim:

1. In combination in a rotor, a hub structure, a plurality of hollow axial flow blades carried on said structure peripherally spaced thereabout and extending radially outward therefrom, each said blade having a blade section at the root end thereof with a substantial curvature along the chord, an element within each said blade fixedly connected thereto adjacent thetip thereof at a point located substantially forward from the trailing edge thereof, said tip being subject to vibration in operation with corresponding movement of said element, each said element extending inwardly of said blade to a locality adjacent the trailing edge of said root end, damper means supported ion' said structure, -said damper means having apart connected totheinner ,end of a, said element for movement therewith in response to said vibration, and a brake part frictionally engageable with said damper means toidissipatev the energyof said movement to damp said vibration.

2. In combination 'in :atrotor, a hub :structnre, a'plurality of hollow axial e'flowblades carried on said structure peripherally spaced thereabout and extending "radiallly outward therefrom, each said blade having a blade -sectionat the root end thereof whose rear portion is directed more nearly parallel to said axis than to the tangent to the mean camber line of said section atthe nose thereof, an element withineach said blade fixedly "ment to damp said vibration.

3. In combination in a-rotor, a hub-structure, a plurality of hollow axial-flow blades carried on said structure peripherally spaced thereabout and extending radially outward therefrom, each said blade having a blade section at the root end thereof with asubstantial curvature along the chord, an element within each said blade fixedly connected thereto adjacent the tip thereof at a point located substantially forward from the trailing edge thereof, said tip being subject to vibration in operation with corresponding movementofsaidelement, each, said element extending inwardly of said blade to a locality adjacent the trailing edge of said root end, damper means supported on said structure, said damper means having a part connected to the inner end of a said element for movement therewith in response to said vibration, and a brake part supported on said structure and movable outwardly under the action of centrifugal force into frictional engagement with said damper means to dissipate the energy of said movement to damp said vibration.

4. In combination in a rotor, a hub structure, a plurality of hollow axial flow blades carried on said structure peripherally spaced thereabout and extending radially outward therefrom, each said blade having a blade section at the root end thereof with a substantial curvature along the chord, an element within each said blade fixedly connected thereto adjacent the tip thereof at a point-located substantially forward from the trailing edge thereof, said tip being subject to vibration in operation with corresponding movement-of said element, each said element extending inwardly of said blade to a locality adjacentthe trailing edge of said root end and displaced in the direction of rotation from said tip point, damper means supported on said structure, said damper means having a part connected to the inner end of a said element for movement therewith in response to said vibration, and a brake part frictionally engageable with said damper means to dissipatethe energy of said movement to damp saidvibration.

References Cited in the file of this patent FOREIGN PATENTS 872j416 Germany Apr. 27, 1953 

